• State Resolved
  • Locked Locked
  • Replies 4 replies
  • Subscribers 79 subscribers
  • Views 2844 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

MSP430F5xx Recommended capacitor at VCORE

Kummi
Mastermind 6220 points
Other Parts Discussed in Thread: MSP430F5521

Hi,

I am sorry to ask the same question...
With respect to MSP430F5521 I would like to know what could happend to the
device if we use 0.1uF instead of 400nF as per the datasheet?

One of our customer has unfortunately designed their product
with 0.1uF capacitor connected to the VCORE pin on MSP430F5521.
But after 3000 hours of usage, one device had a problem on ADC input port and
was returned back for failure analysis.
We came to know that few of the I/O ports are damaged on this MSP430.

So, we would like to know if the improper capacitor connected to VCORE pin
could cause such problem and damage the I/O ports in a long run.
This information is very helpful for us to judge if we should stop the mass production
and re-design the board again.

Best Regards.
kummi

  • 0
    Guru 227245 points
    On the VCORE pin should be a 470nF capacitor and nothing else. The capacitor is used for the internal core voltage regulator that is generating the supply for the CPU core. Having 100nF here means probably an instable core voltage supply, preventing the device from running stable with maximum frequency (for the current voltage setting)
    However, VCORE is not related to the I/O ports.
    Damage on I/O pins happens when overvoltage is fed into the pins. The internal clamp diodes can route up to 2mA rated current to VCC or GND. At 2mA, the diode forward current is >= 0.3V, which gives the VCC+0.3V maximum input voltage in the maximum operating conditions.
    Inputs can be protected by a series resistor. A 1k resistor will enable the inputs to permanently withstand 5V input voltage. (but this will of course increase overall current consumption)
    BTW: there are 470nF capacitors available for 0806 footprint, so maybe you can simply replace the part in your BOM without making a re-design.
  • 0 in reply to Jens-Michael Gross
    Mastermind 6220 points
    Thank you so much for the information.
    We shall try to replace the capacitor.

    Meanwhile, I still wonder what could be the reason for the I/O port damage.
    Because the input voltage applied to the particulat pin(ADC input) is
    around 1.5V, so we believe something else has damaged the I/O port.

    Best Regards.
  • 0 in reply to Kummi
    Guru 33653 points

    As already answered by JMG, VCore cap is not related to PIO damage. At the time, when I made my P2P MSP430F550x boards, didn't have 470 nF cap on hand, so used 220 nF and they worked just fine without problems. Also, I done a lot of bad things (by mistake) to MSP430 devices, including 5V overvoltage, and they survive.

  • 0 in reply to Kummi
    Guru 227245 points
    There are only few things that can damage an MSP port pin. First, a transient that is much faster than the clamp diodes. it could destroy the input gate. Also, HF noise of some energy around the high/low trigger point may cause this, by inducing high cross-currents and transients in the input gate.
    An overcurrent (caused by overvoltage9 that exceeds the 2mA rated current limit on the port pin. This will melt the clamp diodes and either short the pin to VCC/GND or leave the input transistor unprotected. Then even a small overvoltage can damage it.
    Th third thing is loading the pin in output direction with excessive load. If this happens for multiple pins, this may exceed the maximum power dissipation and may rapidly age the output transistors, permanently increasing their on resistance,

**Attention** This is a public forum